Inspiron 1520 Continuous Beep and Keyboard malfunction

Hi,

I am using Dell Inspiron 1520 and I am recently facing an issue in startup. BIOS beep is continuously coming in negligible interval and is moving automatically to select "Internal HDD". After going to windows the "down arrow" is continuously pressed and left corner keys like "esc" "1" are not working.

On connecting external keyboard also the "down arrow" issue is not getting recovered.